If the pulsar beam consists of nested cones, as in [1]}, there may be instances where the leading or trailing part of the cone is below the detection threshold and this would manifest itself as a `partial cone' in the nomenclature of [2]}. In the patchy beam model similarly there may be occasions in which only the leading or trailing part of the beam is illuminated. In the study of 200 pulsars by [2]} they found up to 50 pulsars (25%) could be classified as partial cones with a ratio of approximately 2:1 between pulsars where only the leading edge is seen compared to the trailing edge. These results were obtained largely by comparing the inflection point of the PA swing to the midpoint of the pulse profile. A few years later, [4]} pointed out that, due to finite emission heights, it was expected that the PA swing would be delayed compared to the pulse profile midpoint. In retrospect therefore, we see that many (perhaps all) of the leading partial cones in [2]} are mis-classified once these relativistic effects are taking into account. Furthermore, more sensitive observations carried out on the [2]} sample by [7]} concluded that there were no good examples of the inflection point leading the profile midpoint and that trailing partial cones were not seen.
